The present invention relates to a novel process for the preparation of cyanohydrin esters. More particularly, the present invention relates to the preparation of cyanohydrin esters directly from carboxylic acid anhydrides.
Cyanohydrin esters are important industrial materials both as intermediates to be used in making other compounds and as compounds having utility in and of themselves.
An example of the former is meta-phenoxybenzaldehyde cyanohydrin acetate, which is represented by the formula: ##STR2##
An example of the latter is the pyrethroidtype insecticide represented by the formula: ##STR3##
The compound of formula I can be used as an intermediate cyanohydrin ester from which the insecticidally-active cyanohydrin ester of formula II is prepared, as follows: ##STR4##
This method of preparing cyanohydrin esters of the type represented by compound II presupposes the availability of the intermediate compound I.
The intermediate cyanohydrin ester represented by formula I can be prepared by reacting a free cyanohydrin with acetic anhydride, as follows: ##STR5##
This overall method for preparing cyanohydrin esters of the type represented by formula II is not preferred for two reasons. The first is that it is a two-step process, the first step being the preparation of an intermediate cyanohydrin ester (compound I), and the second step being the further reaction of the intermediate to form the final product. The second objection is that it requires, in the first step, the handling of a free cyanohydrin. Free cyanohydrins are unstable compounds which can release HCN.
It is highly desirable therefore that a method be provided for preparing cyanohydrin esters by a one-step process which does not require the use of free cyanohydrins.